WIP: simplifying vertex packing
simplify with ES6 computed properties
add Style.randomColor to allowed stylesheet macros
switching to master branch of jshint to get support for ES6 computed properties
should switch back to the next released version
move ES6 object iterators to Utils
change ES6 export style for Utils (have to declare var before it can be exported as default)
minor simplification of selection map size
move gl_constants to ES6 module
finish converting geometry construction to new packed vertex layout method:
a new object, GLVertexData, encapsulates a buffer for a provided vertex layout
GLVertexData maintains separate typed array views (as needed by the vertex layout),
and pointers into each view
GLVertexData re-allocates the buffers if they grow too big, then clip them to the final
size when vertex construction is complete